Segments - Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 02, 2021	Oct. 03, 2020	Oct. 02, 2021	Oct. 03, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net sales	$ 10,313,223	$ 4,927,960	$ 26,119,527	$ 14,879,603
Earnings (losses) before income taxes and noncontrolling interests	2,869,107	290,418	6,193,101	617,772
Total assets	24,949,479		24,949,479		$ 20,125,394
Operating Segments [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	6,862,133	2,842,625	17,380,819	8,875,856
Earnings (losses) before income taxes and noncontrolling interests	3,116,539	205,152	6,606,320	512,082
Total assets	12,800,019		12,800,019		9,708,260
Operating Segments [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	2,744,279	1,738,004	6,795,441	4,988,026
Earnings (losses) before income taxes and noncontrolling interests	368,595	186,976	839,737	502,409
Total assets	7,667,192		7,667,192		4,461,042
Operating Segments [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	706,811	347,331	1,943,267	1,015,721
Earnings (losses) before income taxes and noncontrolling interests	161,870	6,232	505,248	(3,068)
Total assets	3,788,291		3,788,291		3,324,489
Intercompany Eliminations [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	1,840,007	731,942	4,561,418	2,264,278
Intercompany Eliminations [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	93,910	51,029	245,523	197,603
Intercompany Eliminations [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	4,355,702	1,863,796	12,011,705	5,772,583
Corporate and Eliminations Items [Member]
Segment Reporting Information [Line Items]
Net sales	(6,289,619)	(2,646,767)	(16,818,646)	(8,234,464)
Earnings (losses) before income taxes and noncontrolling interests	(777,897)	$ (107,942)	(1,758,204)	$ (393,651)
Total assets	$ 693,977		$ 693,977		$ 2,631,603